Washington (CNN) -- The manufacturers of seven caffeinated alcoholic beverages labeled a "public health concern" have stopped producing or shipping the products, the U.S. Food and Drug Administration announced Wednesday.

Last week, the FDA sent warning letters to four beverage makers saying the addition of caffeine to alcoholic beverages was not approved by the agency and it was an "unsafe food additive."

The agency said discussions with the companies resulted in these actions:

-- Phusion Projects of Chicago, Illinois, has ceased producing caffeinated alcoholic beverages, is no longer shipping such products and expects to have all of its caffeinated alcoholic beverages off retail store shelves by December 13. Phusion Projects is the maker of Four Loko.

-- San Diego, California-based United Brands has ceased shipping its caffeinated alcoholic beverage Joose and expects to have its product off retail store shelves by December 13. United Brands also said that it no longer markets Max, another caffeinated alcoholic beverage listed in the warning letter.

-- Charge Beverages Corp. of Portland, Oregon, ceased producing its caffeinated alcoholic beverages, Core High Gravity HG, Core High Gravity HG Orange, and Lemon Lime Core Spiked, in September and has not shipped any caffeinated alcoholic beverages since early November.

-- New Century Brewing of Boston, Massachusetts, has ceased manufacturing its caffeinated alcoholic beverage, Moonshot.

The warning letters last Wednesday followed a year-long review by the FDA, which gave the companies 15 days to either reformulate their products or face possible seizure under federal law, said Dr. Joshua Sharfstein, the agency's principal deputy commissioner. Experts have said the caffeine in the beverages can mask the effects of alcohol, leaving drinkers unaware of how intoxicated they are.

"FDA does not find support for the claim that the addition of caffeine to these alcoholic beverages is 'generally recognized as safe,' which is the legal standard," Sharfstein told reporters. "To the contrary, there is evidence that the combinations of caffeine and alcohol in these products pose a public health concern."

New Century proprietor Rhonda Kallman told CNN last week she was puzzled by the FDA's decision to include Moonshot on its list. Kallman described Moonshot as a craft beer that has about 4 percent alcohol by weight and about two-thirds the caffeine of a cup of coffee, and is sold in only three cities -- "and yet it's being singled out with Four Loko and Joose."

Wednesday, Kallman claimed the FDA has not had a clear policy on caffeinated alcohol. "They have not done their homework," she said. "I'm not going to stop forever."

Moonshot is "absolutely, positively" safe and was marketed to "beer lovers who want a caffeinated choice," she said.

Phusion Projects announced last week that it was dropping caffeine and two other ingredients, guarana and taurine, from Four Loko in the face of "a difficult and politically charged regulatory environment." Four Loko has been nicknamed "blackout in can" by some users.

Sharfstein called Phusion's decision to drop those ingredients a "positive step." And in a statement issued after the decision, the company said it was pleased by FDA's response.

"As we stated yesterday, we have stopped the production and shipment of all our products containing these ingredients," the company said last week.

United Brands previously said it was unaware "of a single incident of injury or other harm associated with its products." The company declined comment Wednesday.

Messages left Wednesday with Phusion Projects and Charge Beverages were not immediately returned.

The FDA began its review in November 2009 after complaints from officials in several states. The controversy exploded last month, when nine underage students at Central Washington University were hospitalized after drinking Four Loko, both on its own and mixed with other drinks, police reported.

Critics say drinks like Four Loko mix caffeine equal to the amount in three cups of coffee with the alcoholic equivalent of three cans of beer and are designed to appeal to younger consumers accustomed to consuming high-caffeine energy drinks. A 23.5-ounce can of Four Loko contains either 6 or 12 percent alcohol by volume, depending on state regulations.

Phusion has compared Four Loko to popular drinks like rum and cola or Irish coffee that also mix caffeine and alcohol. But "we didn't see these kinds of events when people were drinking Irish coffees," Rob McKenna, Washington's state attorney general, told reporters earlier this month.

"What we're seeing now is striking, and we need to take quick action," McKenna said.

Washington and four other states -- New York, Utah, Michigan and Oklahoma -- already had taken steps to remove Four Loko and similar drinks from store shelves. And Gil Kerlikowske, director of the White House Office of National Drug Control Policy, praised the FDA for moving against products he said are "designed, branded, and promoted to encourage binge drinking."